Assessment of Soil Erosion in the Qinba Mountains of the Southern Shaanxi Province in China Using the RUSLE Model

The Southern Shaanxi Province, an important ecological security barrier area in central China, is the primary water source of the south-to-north water transfer project in China. However, severe soil erosion seriously affects the safety of regional ecological security and water quality of the water diversion project. To reveal the characteristics and variation of soil erosion in the southern Shaanxi Province after the implementation of a series of eco-environmental construction measures, in this study, the spatio-temporal characteristics of soil erosion from 2000 to 2014 were evaluated based on the Revised Universal Soil Loss Equation (RUSLE) model and Geographic Information Systems (GIS). The average soil erosion of southern Shaanxi Province in China was characterized as slight (less than 500 t·km–2·a–1) and mild erosion (500–2500 t·km–2·a–1) with an average soil erosion modulus of 1443.49 t·km–2·a–1, 1710.49 t·km–2·a–1, 1771.99 t·km–2·a–1 and 1647.74 t·km–2·a–1 in 2000, 2005, 2010 and 2014, respectively. The results revealed an increase in soil erosion until 2000 and a mitigation during the period of 2000 to 2014. After 2010, the soil erosion was controlled effectively. The spatial distribution of soil erosion displayed obvious spatial heterogeneity, and the high soil erosion (greater than 2500 t·km–2·a–1) was primarily distributed in the north-central and south counties of the study area. The soil erosion remained high and aggravated in six counties (i.e., Zhen’an, Zhashui, Ningshan, Ningqiang, Lueyang and Shanyang), and high erosion (greater than 5000 t·km–2·a–1) was found in the regions with slope gradients greater than 35 degrees and the middle mountainous (800–2000 m) regions. Therefore, the eco-environmental construction measures could effectively control soil erosion. However, unreasonable human activities remain the primary cause of soil erosion in the southern Shaanxi Province. In the future, more comprehensive and thorough ecological construction measures will be necessary to ensure regional ecological security and the eco-environmental quality of water sources.